3) If the material is transparent, it always uses the alpha channel of diffuse right? (what about specular + transparent? as far as i remember for low light settings, the spec map is copied to the alpha of the diffuse and for high light in the alpha of the bump/normal map)

4) is there any other way to make the material transparent?

5) do you think it would be ok if i don't differ between all the transparency variants and make it just transparent for all of this options in my viewer??

Double-sided transparency is the same as single-sided but it doesn't have the back-face culling.

It's worth noting that all polygons by default have back-face culling; the only ones that really don't are ones with double-sided transparency.

Anakin wrote:2) Are there other ways to make something transparent??

Like through an option file? I don't believe so, no. Although you can actually use vertex colors to drive the transparency values of a mesh by putting giving the mesh a Color At Vertices property in XSI and setting the material to use some-sided transparency with additive transparency, like I did by overlaying a layer of polygons over the floors and walls to get this neat frozen effect here:

Vertex colors in XSI:

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In-game:

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Diffuse texture's alpha channel:

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And to get this force field effect here:

Vertex colors in XSI:

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In-game:

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Diffuse texture's alpha channel:

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So as you can see, the color of a vertex drives that vertex's opacity, where the combined RGB value of the vertex's color = the vertex's opacity. (i.e. the brighter the vertex's color, the more opaque it'll be; and the darker the vertex's color, the less opaque it'll be)

With that said, this is done alongside the vertices' transparency being affected by the diffuse's alpha channel. It's done in two passes:

Anakin wrote:3) If the material is transparent, it always uses the alpha channel of diffuse right?

Correct.

Anakin wrote:what about specular + transparent?

I believe it still uses the diffuse texture's alpha, correct.

Anakin wrote:4) is there any other way to make the material transparent?

No.

Anakin wrote:5) do you think it would be ok if i don't differ between all the transparency variants and make it just transparent for all of this options in my viewer??

I recommend rendering additive transparency as whatever-sided transparency the material has. (so basically you should just ignore whether or not there's additive transparency - unless you want to implement the technique I mentioned in response to question 2)